In recent years, various systems have been devised for monitoring functions and controlling functions on the various cars assembled into a railroad train of the intercity as well as intracity variety. These systems have been designed to perform various special functions, generally including, for example, interrelated control of multiple locomotives, monitoring of various critical operating parameters on the various cars of a train, and communication between various cars to permit some degree of monitoring, in the lead or drive vehicle of the train, the critical functions which can affect train operation or which involve safe operation of the train.
Numerous patents have issued to systems of these general types, including systems in which multiplex communication between cars is employed, and examples of these include the following patents:
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While this is by no means an exhaustive list of the art in this field, these patents represent and constitute examples of the development which has occurred.